FuckFastCGI

Description

This is a php script to exploit fastcgi protocol to bypass open_basedir and disable_functions.

It will help you to bypass strict disable_functions to RCE by loading the malicious extension. While the original exploit loads an external lib, which must be compatible with the current installation, my exploit is pure PHP

Version 1 - Similar to the original FuckFastCGI, but made simpler

• Update the config between the markers:

// ---- BEGIN CONFIG
$ext_dir_path = '/tmp';
$ext_name = 'hello.so';
// ---- END CONFIG

• Also update the socket path:

$client = new FCGIClient("127.0.0.1:9000", -1);

or (should be a symlink to the real socket)

$client = new FCGIClient("unix:///var/run/php/php-fpm.sock", -1);

Compared to the original exploit, it requires only one PHP to work, based on this exploit.

Also, if it runs < PHP8, the file hello.c must be slighty modified, line 28: the value TSRMLS_CC should be uncommented. Otherise compilation will fail (https://stackoverflow.com/questions/66194531/how-to-compile-php-module-in-php8-0-that-used-to-use-tsrmls-cc-in-php7-but-is-d)

I put a Docker config to test it.

First the evil *.so should be built:

• run docker-compose up --build
• then open a shell on the container and browse to /tmp/ffcgi/ext_example/system
• run the following commands (can be challenging in a real-life scenario, because it requires a machine with the same setup as the victim...):

$ cd /tmp/ffcgi
tmp/ffcgi$ phpize //requires php-dev package
tmp/ffcgi$ ./configure
tmp/ffcgi$ make //a 'make clean' may be required in between
tmp/ffcgi$ cp modules/hello.so ../

Now browse to the PHP exploit file (localhost:8081), and pass a cmd GET parameter. If it fails, it would be worth trying to refresh, it happens sometimes when the first request after a reboot contains the cmd parameter, dunno exactly y

Try to run phpinfo from the main script, it will indicate that all exec-like routines are disabled.

Now, to make it work on a victim server:

• upload thedocker/code/index.php in a writeable directory
• upload the *.so in the folder $ext_dir_path

Version 2 - Make it work without external library

Why make things even more complicated, when we can keep them simple ? The only_php version works by modifying the MTA path ... No need to upload an evil *.so now